Concrete construction forms are generally prefabricated by the manufacturer for use in a particular structural application such as corner forms, linear wall forms, or form parts for assembly on the job to build structures having a curved surface and the like. Thus, in U.S. Pat. No. 2,616,148, a form assembly enables the casting of generally curved surfaces to a particular desired curvature by the use of flexible metal sheets arranged with their side portions in an overlapping relation and having reinforcing members at such side portions that are adjustably clamped to a supporting scaffold to secure the flexible sheets in the desired curved pattern to form an arched roof. Arched roof constructions are also shown in U.S. Pat. Nos. 2,436,543 and 2,933,056.
U.S. Pat. No. 3,971,176 discloses a permanently formed wooden stud-truss that has a curved central arch section positioned between a pair of straight end sections. The central arch has transverse slots or notches the sides of which are moved into contact engagement to provide the desired curvature. Before being closed the slots are filled with an adhesive compound to maintain the central arch in permanent deflection.